The present invention relates, in general, to optical interconnect of electronic modules, and more particularly, to a novel technique that provides optical interconnect which can be easily separated from the module and accurately reconnected to the module.
Optical fibers had been used in the industry for coupling signals between electronic modules. Since optical fibers accommodated more signals and operated at much higher bandwidth than electrical cables, optical fiber interconnect of electronic modules gained acceptance in the industry. In most cases, the electronic modules included a printed circuit board that had electronics mounted on the board, and a cover to protect the electronics on the board. Generally, semiconductors that emitted or detected optical energy were attached to the board and electrically connected to the electronics on the board. Previous methods for coupling semiconductor emitters or detectors to optical fibers primarily involved one of two techniques. One technique used V shaped grooves etched in a plate as an alignment mechanism. With this technique, an array of emitters was attached to a circuit board. Then an array of optical fibers was attached to the V shaped groove whose periodicity matched that of the emitter array. The alignment plate and attached fibers were then carefully moved around until the fibers aligned with the emitting array. When alignment was achieved, the plate was attached to the board with the grooves in the plate holding the fibers in place. A similar technique was used to align a detector array. Another technique used a package, similar to a 16 pin dual in line semiconductor package, as the alignment structure. An emitter and an imaging lens were mounted in the package, and the lens was aligned to the emitting area of the emitter. An optical fiber was inserted through an opening in the package while guides in the package guided the optical fiber to the lens. A similar technique was used for a detector.
Neither technique provided highly efficient optical coupling that was easily repeatable. Efficient coupling of an emitter to an optical fiber requires alignment tolerances of less than one micron, while efficient coupling of a detector to an optical fiber requires alignment tolerances of approximately one micron. Previous techniques could not repeatedly provide such accurate alignment. Consequently, the coupling of previous alignment techniques was sometimes inefficient. Additionally, the alignment components and the alignment procedures of previous techniques were expensive. For the electronic modules that used the previous optical interconnect methods, removing the cover of the electronic module for maintenance or repair of the electronics, can easily disturb the alignment and reduce the efficiency of the coupling.
Accordingly, it would be desirable to have an optical interconnect for electronic modules that provides high efficiency coupling between an optical fiber and a semiconductor emitter or detector, that provides accurate realignment after the module has undergone maintenance or repair, and that reduces the cost of the optical fiber interconnect.